The design of general electromagnetic servers usually employs a spring force to control the closing of valve openings. And an electromagnetic coil is used to control the opening and closing the valve openings. When conveying goods enter into the valve, the positive pressure must be controlled to be less than the bucking force of the spring. Otherwise the valve cannot be closed completely. Hence the bucking force of the spring must be increased. However, to achieve this end also has to increase the capacity of the electromagnetic coil and result in a greater size for the server. Such a structural problem mainly is caused by a positive pressure or a negative pressure exerting on the valve stem that cannot be offset. Improvements taken by producers often focus on the size of the spring or the electromagnetic coil. The basic problem remains unresolved. It baffles producers and creates a lot of problems. The accuracy of valve control also is affected. Therefore to eliminate the positive and negative pressure applying on the valve stem to achieve a no loading state is the goal of the invention.